Multiplexer for controlling and monitoring coded key operated accesses

ABSTRACT

A multiplexer for scannings a plurality of controlled accesses, or doors, for determining if access or entry has been attempted. The scanner is coupled to a multiplicity of such accesses for determining if a key has been placed in its receptacle for operating a controlled latch. The key is preferably an electrical key having unlocking and identification information recorded thereon. If a key-in condition is determined, the scanner is momentarily stopped to allow the information derived from the key to be processed for determining the validity of the unlocking information and the key user identification information. This I.D. control information is also recorded for providing a record of the key usage relative to the time of day, the door and the recorded control information. If the control information is completely valid as to the unlocking information and the identification information only, then is the controlled latch operated.

United States Patent Hedin et al. [451 June 27, 1972 [54] MULTIPLEXERFOR CONTROLLING Primary Examiner-Donald J. Yusko AND MONITORING CODEDKEY y g and OPERATED ACCESSES ABSTRACT [72] Inventors: Robert A. Hedln;Everett E. Dukes, Jr.,

both of Yorba Linda, Calm A multiplexer for scannings a plurality ofcontrolled accesses,

or doors, for determining if access or entry has been at- AssigneelEaton Corporation, land, Ohio tempted. The scanner is coupled to amultiplicity of such accesses for determining if a key has been placedin its recepta- [22] Flled' April 1971 cle for operating a controlledlatch. The key is preferably an [211 App]. No.: 135,265 electrical keyhaving unlocking and identification infonnation recorded thereon. If akey-in condition is determined, the scanner is momentarily stopped toallow the information [52] U.S.Cl. ..340/l47 R, 340/149 R,3l77/l23748,derived from the key to be Processed for detcrmining the validity of theunlocking information and the key user identifi- Eg "G06k 17/ 2 cationinformation. This 1D. control information is also recorded for providinga record of the key usage relative to 56] Reknnces Cited the time ofday, the door and the recorded control information. If the controlinformation is completely valid as to the UNITED STATES PATENTSunlocking information and the identification information only,

then is the controlled latch operated. 3,590,333 6/1971 Blum ..340/149 AX 12 Claims, 4 Drawing Figures "fjjjff jf j (0/?R7' 000; 5/94/42 f F a"1 lIJmTwwr s-wl I 1.0, l'flMd/Mf/m/ flan 71402450 I i ii' rm T. 1.0047;: I I 0,414 0mm: zflfcf/ I i 7-0 MW rm l i L5 m l i I l M64 WPflA/firaw/4mm? i I onrn xv/u/o my 1 I [my W7 KEY 9 kiV/A/ i I L L-L f l 4 p ii pi, /;H/5 l7' :7

MW!) 1 anrrs CO/i/T/WL I 1 man/6 mus. VAL/D K6) la 5Z0 L i a e our :0-we [)flufl'fl D604 s it 4A5 fi 110 m/ a 99 /f//l/f[/( +1 l i l L l i I,5'64/1/ 4M4 i 513% (a W4 jam/M I I ZZ/Z'IMW 1 11am /.0. L 4 1 i Jyefl/zmlsi- 6 {gig/656' PATt'NlEuauuzv m2 SHEET 1 OF 4 |||L I I I I I Ill MULTIPLEXER FOR CONTROLLING AND MONITORING CODED KEY OPERATEDACCESSES This invention relates to multiplexing apparatus and morespecifically to multiplexing apparatus for scanning a multiplicity ofcontrolled accesses or doors for monitoring the operation of theaccesses or doors and recording same. i

The present invention in some of its aspects is related to the copendingapplication bearing Ser. No. 35,061 and entitled ELECTRONICIDENTIFICATION KEY ACTUATED CON- TROL SYSTEM.

At the present time there is in commercial use electrical keys forelectrically controlling a door latch or similar apparatus wherein anelectrical key is operative for locking and unlocking the latch. Onesuch electrical key that has been extensively used is the subject ofU.S. Pat. No. Re. 27,013 granted on Dec. 22, 1970, and based on US Pat.No. 3,392,558 granted on July 16, 1968. In this type of electrical key,the key itself is constructed of an electrical insulating materialhaving a preselected number of open and closed conductive circuits orsegments recorded thereon for defining a particular combination forunlocking a latch by means of a control circuit operative with the key.The control circuit is generally defined in terms of a logical networkfor decoding the pattern of conductive and non-conductive signals fordetermining whether or not the key is valid or if it has the correctcombination for unlocking the controlled latch. It will be recognizedthat in this type of apparatus each key for a particular door will havea unique combination of circuits so that it will only be operative for aparticular controlled access or door. This type of key has been furtherdeveloped wherein the key also includes user identification informationrecorded thereon whereby each individual user is issued a key for aparticular controlled access having a unique identification informationor an identification number recorded thereon. The identificationinformation is also recorded on the key in terms of preselectedcombination of conductive and nonconductive circuits or segmentsthereon. The control circuitry for such a key having unlocking andidentification information recorded thereon has been developed so thatdespite the fact that the key may have the correct unlocking informationthereon, if the identification number is not valid, the key having aninvalid identification number will not be operative for operating alatch. Key identification numbers may be rendered valid or invalidreadily by means of associated electrical apparatus. This type of key isdescribed in detail in the copending application bearing Ser. No.35,061.

When an installation requires a large number of such electrical keys, ithas become advantageous to be able to monitor the operation of thecontrolled accesses or doors and to record the fact that a key has beenemployed in an attempt to operate a latch or the like. It is furtherdesirable to 'not only record the fact of the key insertion and theoperation of the latch but also to record the identification oridentification number of the individual using the key and whether or notthe key is a valid key relative to the door it is employed with. In alarge structure such as an office building, for example, there is a needfor monitoring the operation of the doors at all of the various officesand to record the time of use and point of use of the various keys thatmay be attempted to be employed at the various doors. It has been foundto be relatively expensive to monitor these operations and record theevents at a .controlled access by employing a recording device orprinting device associated with each door. Accordingly, at the presenttime there is a need for a relatively inexpensive, simple multiplexingapparatus for monitoring a multiplicity of controlled accesses forallowing the recording of the operations of the lock at the controlledaccess or door preferably by means of a printer. It is also desired tonot only identify the fact that a particular latch has been operated butalso the individual opening the latch or attempting to open the latchand the particular time of day the entry was made or attempted.

The present invention provides a relatively inexpensive and simplemultiplexing apparatus that allows a multiplicity of controlled accessesor doors to be continuously scanned at a relatively high speed and allowthe recording of the insertion of a key into a door in an attempt tooperate the latch. The apparatus of the present invention may scan at arelatively high speed up to 40 doors or controlled accesses and recordthe desired operational information for the particular access. Theapparatus of the present invention further allows the operator to voidout or render invalid any particular key for a controlled access for apreselected period of time or for an indefinite period and then recordany attempt to use an invalid key or a key having the wrong unlockingcombination.

The multiplexing system of the present invention comprises a pluralityof controlled accesses each having a latch and a key operable withcontrol circuit means for unlocking the latch. The keys operable withthe control means preferably have preselected combinations of controlactuation information recorded thereon unique for operating the controlmeans of a particular controlled access for unlocking the latch andpreselected identification or identification information wherein the ID.information is unique to a particular user to whom the key is issued. Inorder to unlock the latch, then, each access must be operated by a keyhaving the correct unlocking information and the correct identificationinformation and which identification information may be selectivelyrendered valid or invalid. Associated with each such controlled accessis a high-speed scanning apparatus which is coupled to each controlledaccess for scanning and signalling the presence of a key in thecontrolled access. The scanning apparatus is controlled to continuouslyscan each controlled access and upon sensing the presence of a key atany one access or door the scanner is caused to momentarily stop thescanning operation. During the interval that the scanner is momentarilystopped the key information is sensed to determine the validity of thekey from both the standpoint of the combination of unlocking informationand the user identification information. If all of the information iscorrect and the key is determined to be a valid key the controlled latchis unlocked. As a result of the sensing of a particular key-incondition, the identification information along with the determinationof the validity of the key is presented to the recording apparatus orprinter for printing out the fact that the key has been attempted to beemployed at the particular door or controlled access along with theidentification information of the point of use of the key or dooridentification. The scanner is controlled so that during the intervalthat the printer is printing out the information relative to the key-incondition it can continue to scan the remaining controlled accesses.During successive scanning intervals the scanner may once again sensethe previous key-in condition and for this purpose control apparatus isprovided for inhibiting the recording of the same usage of a key toprevent the excessive redundant recording of information. Specifically,in the event that a key is maintained in its receptacle for an extensiveperiod of time or an electrical malfunction results in the same type ofsignal being coupled back to the scanner, a keyin timer is provided forsensing such a long time interval and rendering the printer inoperativefor printing out the information at a particular door and allow theprinting to continue at the other doors. The control apparatus alsoincludes means for sensing the operation of the printer and in the eventit malfunctions, eliminates the printer operations to allow the scannerto continue to scan the various doors.

These and other features of the present invention may be more fullyappreciated when considered in the light of the following specificationand drawings, in which:

FIG. 1 is a block-schematic diagram of the multiplexing system embodyingthe present invention for a single controlled access or door;

FIG. 2 is a block diagram of a printer that may be employed Themultiplexing system of the present invention can be most readilyappreciated when the multiplexing system is implemented in terms of theelectrically controlled latches which is the subject of theaforementioned U.S. Pat. No. Re. 27,013 and the type of keys disclosedin the copending patent application bearing Ser. No. 35,061. It will berecognized that the aforementioned copending patent application includesthe basic features of the particular electronic lock and key that is thesubject of U.S. Pat. No. Re. 27,013. This patent discloses an electricalkey wherein the key is basically defined on an insulative substratecarrying a plurality of conductive and nonconductive segments recordedthereon and arranged in a preselected pattern or combination forunlocking a particular latch. The key is insertable into an energizablereceptacle for providing a plurality. of output signals from thereceptacle in accordance with the pattern of segments recorded thereon.The signals derived from the receptacle are representative of thepattern of conductive segments on the key and are coupled to a sensingcircuit which may be a logical circuit for determining the validity ofthe combination on the key for operating the latch. This type of key andcontrol apparatus is employed in the present invention. If a moredetailed disclosure of this type of key and control apparatus isrequired, reference may be had to U.S. Pat. No. Re. 27,013 which isincorporated herein by reference. The type of electrical key employedfor the purposes of the present invention also incorporates theteachings of the copending application bearing Ser. No. 35,061 in thatthe key is also constructed as including user identification informationor ID. information. The key, then, is operable only for unlatching adoor or controlled access when the key includes not only the correctunlocking information but also a valid identification number. Thedetermination of the validity of the identification number may also beeffected by means of sensing circuits employing logical networks as morespecifically described in the aforementioned copending Patentapplication Ser. No. 35,061. It will be recognized that the keys per sedisclosed in the latter mentioned copending application are not thesubject of the present application.

To further facilitate the understanding of the present invention therecording apparatus employed for the purposes of the present inventionmay be the type of printing apparatus described in said copendingapplication bearing Ser. No. 35,061. In particular, the printing unit isa commercially available printer which is described in the copendingapplication as being available from the Datatotal Company and now knownas the Hecon Corporation, 31 Park Road, New Shrewsbury, NJ. Theparticular feature of this printer is that it can be advantageouslyemployed to not only record the information as to usage of the key butalso may be readily adapted for rendering certain identification numbersvalid or invalid. The present invention will be described on the basisof the structure for recording and voiding out identification numbers asspecifically disclosed in the copending application and morespecifically FIG. 5 thereof. For the purposes of the present inventionthe information derived from the printing unit includes the electricalsignal indicative that a key inserted has a void identification numberand also the print command that is applied to the print hammer(identified as the hammer 71 in the copending patent application) forprinting out all of the information once the printing wheels have beenrotated to the correct character for printing out the sensedinformation. This print command signal and the signal indicative of avoid identification number is utilized in the control apparatus for thepresent invention and the detailed disclosure with respect to theprinter and its associated operations are incorporated herein byreference from the copending patent application bearing Ser. No. 35,061.

The aforementioned copending application bearing Ser. No. 35,061 alsodiscloses and claims an elementary multiplexing system incorporatingprint-out or recording of key and user information of the type underconsideration by the present application.

Now referring to FIG. 1, the general organization of the multiplexingapparatus of the present invention will be examined. The generalorganization illustrated in FIG. 1 is directed to the multiplexingoperations as it applies to a typical controlled access or door. It willbe recognized that the multiplexing operations will be the same foradditional doors.

For this reason, then, each controlled access or door will have a doorlatch control A and a door circuit B that is associated with the scannerC for time sharing a printer D. It will be recognized that the scanner Cis effective for providing unique signals for sequentially scanning eachdoor latch control A to determine whether or not a key is in thereceptacle. If it is determined that a key is in, the scanner is adaptedfor deriving the information recorded on the keys and for printing outsame at the printer D. In this fashion the scanning element C may beutilized for all of the controlled doors and a single printer D is timeshared in accordance with the present invention. As indicatedhereinabove the door latch control A comprises an electricallycontrolled latch 10 controlled by means of the electrical key 11 havingunlocking information and ID. information recorded thereon as disclosedhereinabove and in particular in U.S. Pat. No. Re. 27,013 and theaforementioned copending application bearing Ser. No. 35,061. The key 11 is associated with the key receptacle 12 for receiving the key 11therein and the placement of the key in the receptacle allows theinformation coded on the key for unlocking the latch and providing theID. or identification information to the printer D for recording thefact of the placement of the key 11 in the key receptacle 12 or thekey-in" condition. The combination data or the unlocking data derivedfrom the receptacle 12 is applied to a combination decoding element 13associated with the control latch 10 for operating the latch only when avalid key signal is provided therefrom. The valid key signal in thisinstance comprises not only the correct combination or unlocking datafrom the key 11 but also the correct I.D. data. The determination of thevalidity or invalidity of the identification information is derived fromthe printer D and is utilized in combination with the conventionallogical circuits described in the aforementioned reissue patent and thecopending application for providing the valid key output coupled tooperate the control latch 10. The structure described with respect tothe door latch control A is defined in accordance with the structuresdisclosed in the aforementioned reissue patent and the copending patentapplication and as I combination disclosed herein.

Each controlled access or door also has a door circuit B for receivingthe information from the door latch control A in response to the signalfrom the scanner C for application and processing by the printer D. Thedoor circuit B is defined for responding to a decoded door signal fromthe scanner C that is unique to the particular door or controlledaccess. The door circuit B includes the inhibit gates 14 which receivethe ID. data derived from the key receptacle 12 of the door latchcontrol A. In addition, the inhibit gates 14 receive the outputindication from the combination decode element 13 indicative that thekey in the receptacle 12 has a wrong unlocking combination thereon. Theinhibit gates 14 are defined for receiving the indication from thereceptacle 12 that key 1 1 has been inserted into a receptacle or akey-in" signal. It will be recognized that for this purpose the inhibitgates 14 comprise an individual inhibit circuit for each data bit orpiece of information applied to the gates 14. The gates 14 are definedso that they inhibit any information applied thereto from appearing attheir outputs in the absence of a decoded door signal from the scannerC.

The control of the inhibit gates 14 is under the control of a decodeddoor signal from the scanner C and a logical network identified as theinhibit gates control 15 provided with each door circuit. The inputsignals to the inhibit gates control 15 are the signals derived from thegates 14 indicative of the signal that the key 1 1 in the receptacle 12has the wrong combination as well as the signal from the printer D thatthe key 1 1 in the receptacle 12 has a void ID. number. In the eventthat the combination recorded on the key is correct and theidentification number is correct the inhibit gate control will couple asignal back to the door latch control A and specifically the combinationdecode circuit 13 for logical coinbination with the combination data toprovide the input indication to the element 13 for deriving the correctcode signal from the element 13 to operate the latch 10.

The scanner C comprises a scanning element 16 under the control of ascanner control element 17. The scanner 16 may comprise a binary codeddecimal counter having a binary to decimal decoder coupled thereto forproviding a decimal output indication or a unique signal representativeof each count of the counter. The counter is under the control of thescanner control element 17 and continually pulses or counts up thecounter to cause the plurality of the unique output signals to begenerated from the scanner 16 for the purposes of scanning ordetermining the key-in condition of each door controlled by the scannerC. For this purpose, the key-in signal is applied to the scanner controlelement 17 from the inhibit gates 14 when a key is sensed as being inthe receptacle 12. The key-in signal applied to the scanner control 17is effective for stopping the scanner 16 or stopping the countermomentarily to allow the information to be derived from the keyreceptacle 12 and processed and printed out by the printer D. At thecompletion of the printing operation, the printer D will pro- I vide asignal identified as a print command" to the scanner control element 17that will reactivate the scanner to allow it to continue to scan theremaining doors. It will be recognized that each decimal output signalfrom the scanner 16 is uniquely coupled to a particular door circuit forsensing the presence or absence of a key in the correspondingreceptacle. If there is no key in the receptacle for a particular doorthe scanner is pulsed to the next count so as to scan the successivedoor and to successively and continuously scan for each count of thecounter and recommence its scanning operation at door 0" after themaximum count of the counter is reached.

The printer D is shown in broad block form in FIG. 1 and in moredetailed block diagram form in FIG. 2. It will be recognized that theprinter D is the printer identified hereinabove that is commerciallyavailable from the Datatotal Company, now known as the Hecon Corporationof New Shrewsbury, NJ. in addition it will be recognizedthat thedetailed implementation and operation of such a printer is described inthe copending application bearing Ser. No. 35,061. The description ofthe operation and the structure for this printer from said copendingapplication is incorporated herein by reference. For the purposes of thepresent invention, the printer D can be considered as comprising themajor elements as'particularly identified in FIG. 2. The printer Dcomprises the ID. decode element 18 associated with the ID. void element19. The 1D. decode element is responsive to the key identification datareceived from the inhibit gates 14 of the door circuit B. The ID. decodeelement 18 receives the generated binary coded decimal bits from theinhibit gate 14 and decodes it into decimal form. This information isapplied to the print control element 20 for the print wheel associatedwith the print hammer for printing out the decoded decimal informationderived from the key 11 in the receptacle 12. The print wheel and printhammer are illustrated in block form and identified in FIG. 2 by thereference numeral 21. The operation of the print wheels is such thatwhen the print wheels are rotated in the correct relationship withrespect to the print hammer a print command is generated to cause theprint hammer to strike the print wheels for printing out the charactersopposite the hammer on the record medium. Specifically, the characterson the periphery of the print wheels will be rotated until theparticular decimal information decoded from the element 18 is in aposition to be printed out by the hammer of the printing element D.

The print control 20 is also responsive to a key-in signal derived fromthe individual inhibit gates of the inhibit gates 14. The door 1.D.signal and the wrong combination signal are also coupled to the printcontrol to allow the printer D to print out the door identification aswell as the wrong combination in response to the placement of a key 11in a receptacle 12 for a controlled access.

Another important aspect of this type of operation is the ability todetermine from the 1D. data whether or not the key has a valid ID.number. For this purpose the decoded 1D. data from the element 18 isutilized by the LD. void element 19 to determine the validity orinvalidity of the ID. information. If the ID. void element 19 determinesthat the LD. recorded on a key 11 is void it produces an output signalthat is coupled back to the inhibit gates control 15 of the door circuitto prevent the latch 10 from being operated.

With the above general organization in mind, the operation of themultiplexer can be examined. The operation is such that the scannerelement 16 is continuously under control of the control element 17 tocause the scanner 16 to continuously produce decoded door signalstherefrom. With no keys placed in the receptacles for any of the doorcircuits, then, the scanner continuously produces output signals inaccordance with the maximum count capacity of the scanner and uponcompletion of its count will recycle or recommence its count.Accordingly, the unique signals from the scanner C are coupled to eachof the controlled door circuits, and ,40 such decoded signals areindicated in FIG. 1. For the purposesof understanding the presentinvention, it will be assumed that a key 11 having the correct unlockingcombination data recorded thereon and the correct 1D. data thereon isplaced in the key receptacle 12. The door circuit B will be consideredrelative to the decoded door signals from the scanner C to be door 0.With the placement of the key 1 1 in a receptacle 12, then,thevcombination data derived from the receptacle 12 is applied to thedecoding network 13. 1n addition, the 1D. data is applied to the inhibitgates 14 for the door circuit B. It will be recognized that although akey 11 has the correct unlocking combination data recorded thereon thatthe combination decode element 13 will not operate a latch 10 until itreceives the indication from the inhibit gate control 15 that the key isa valid one, i.e., the ID. number is correct. The 1D. data, along withthe key-in signal, then, is applied in parallel circuit relationship tothe gates 14. This infonnation will not be available at the outputs ofthe inhibit gates 14 except when a decoding door signal unique to theparticular door is applied to the gates 14 for rendering themconductive. In this instance, then, when the scanner 16 provides the 0door signal the ID. data from the door latch control A and the key-insignal from the receptacle 12 and the wrong combination signal from thecombination decode element 13 will all be available at the outputcircuits from the inhibit gates 14. The key-in signal will be applied tothe print control element'20 as well as to the scanner control element17. The detection of the key 1 1 in the receptacle 12 by the 0 doorsignal appearing at the inhibit gates 14 will cause the scanner control17 to stop the scanning operation or stop the counting up of the counterto maintain the decoded door signal at the 0" door. At this time, theID. data along with the door number or ID. is coupled to the printer Dalong with the key-in signal and the wrong combination indication. Thiswill cause the printer to print out the door number, the key ID. numberand the time of day, or any other information required to be identifiedfor controlling the door circuit B. If the 1D. void element 19determines that the ID. number is void, a void 1.D. signal will beapplied from the inhibit gates control 15. Ifthis condition exists,then, the correct code signal from the combination decode element 13will not be generated and the latch 10 will not be operated. Since it isassumed that the ID. number is valid, a void I.D. signal will not begenerated and since neither the void 1.D. signal nor the wrongcombination signal is applied to the inhibit gates 15, a valid keysignal will be generated and applied to the decode element 13. This willcomplete the logical combination of the correct input indications to thecombination decode element 13 to allow it to produce a correct codesignal for the controlled latch 10 to operate same. Along with theinitiation of the print-out of the information from the printer D, thesame print command signal is coupled back from the printer D to thescanner C. Specifically, the print command signal is applied to thecontrol element 17 to reactivate the counter to cause the scanner tocontinue its scanning operation.

Now referring to FIGS. 3 and 4 the detailed organization of themultiplexer of the present invention represented by the block diagram ofFIG. 1 will be described for providing the signals to the printer D asrepresented in FIG. 2. FIG. 3 illustrates in logical-block diagram formthe multiplexer as it is applied to a plurality of controlled doorsidentified as the doors 0, l, 2, 3, up to 40 controlled doors. It shouldbe recognized that the door circuits B described in connection with FIG.1 are the same for each of the controlled doors 0, I, 2, etc., asdetailed in FIG. 3. The typical door circuits illustrated in FIG. 3include further features relative to the control of the data from theinhibit gates 14 that are not apparent from the comprehensiveorganization illustrated in FIG. 1. Each particular door circuit asillustrated in FIG. 3 includes within the inhibit gates control a key-intiming element 40 for determining when a key 11 remains in itsreceptacle beyond a predetermined time interval to allow the multiplexerand the printer D to continue its scanning operation without theprinting out of redundant data. Once a key has been sensed as being in aparticular door and the information relative to the key has been printedout by the printer D without the removal of the key for a time intervalthat allows the scanner D to return to the same door, the invention isdefined to prevent the print-out after a set time interval of theinformation relative to such a key retained in a receptacle. A key-intimer 40 provided for each door circuit B allows the scanner to continueto operate and prevent the printer D from printing out the sameinformation continuously.

It facilitates the understanding of the logical-block diagram of FIG. 3if the detailed implementation of the inhibit gates 14 is firstconsidered. This consideration is relative to the circuit diagramsillustrated in FIG. 4 and the logical-control gates associated'with thegates 14. As indicated hereinabove, the inhibit gates 14 comprise aplurality of gates for individually receiving in parallel circuitfashion the data bits from the key receptacle 12. Each inhibit gateincludes a transistor switch having its emitter lead connected directlyto ground and its collector lead connected as an output element for thegate. The base lead for each transistor gate is connected in common tobe responsive to the door I.D. signal derived from the scanner C. Thedata bits are applied to the inhibit gates by means of input circuitsdefined by means of the base-emitter circuit so that in the normalconductive conditions of the gates 14 no output indication is derivedfrom any of the gates in the absence of a door I.D. signal applied tothe respective base leads. Stated differently, the data bits appliedfrom the key receptacle 12 do not appear at the output circuits of theindividual gates until a door I.D. signal is received therefrom. Asindicated in FIG. 4, for the purposes of determining the ID. number of akey in a receptacle 12, the ID. data bits are recorded on a key in termsof the binary coded decimal 8-4-2- 1 notation. Accordingly, anindividual gate is connected to be responsive to each of thecorresponding data bits arranged in the 8-4-2-1 notation derived fromthe receptacle 12 for providing the appropriate signals therefrom inresponse to the triggering thereof. In the same fashion, an inhibit gateis provided for the key-in signal from the receptacle l2 and the wrongcombination signal derived from the combination decoding element 13 ofthe door latch control A. It will be recognized with respect to the ID.data bits, the same pattern of binary bits that appear on the key willbe electrically represented on the output circuits for the 8-4-2-1 gatesof the gating element 14. The presence of the correct door I.D. signal,then, at the inhibit gates 14 will be effective for coupling out thedata bits, key-in, and wrong combination applied to the gates 14 in aparallel circuit relationship for application to the control gates 15and to the printer D. For this purpose each of the inhibit gates 14 foreach door circuit B is coupled to an individual OR circuit arrangedbetween the outputs of the inhibit gates for each of the door circuitsand'the input to the ID. decoder 18 of the printer D. For example, the ldata bit of the ID. data bits is applied to the "OR" circuit 30 alongwith the 1" data bits from the remaining controlled door circuits asdiagrammatically represented in FIG. 4. In the same fashion, individualOR circuits 31, 32 and 33 are provided for the .2, 4" and 8 data bitsand their output circuits are coupled to the I.D. decoder 18 forproviding the decimal output indication corresponding to the binarycoded data bits applied thereto. 7

The key-in signal applied to the individual key-in inhibit gate of thegates 14 appear at the output of the gate in response to the receptionof a door I.D. signal and is applied to the printer control element 20,as best appreciated from FIG. 2. In the same fashion, the wrongcombination signal will appear at the output of the wrong combinationinhibit gate in response to the door I.D. signal. The wrong combinationsignal is applied to an OR gate 34 of the inhibit gate control element15 along with the wrong combination signals from the remainingcontrolled doors. The output of the OR gate 34 indicative of the wrongcombination from any one of the doors is applied to an emitter followercircuit 35 and then to the printer control element 20 and the no-errorNOR gate 36. The emitter of the emitter follower circuit 35 is alsoresponsive to the void I.D. signal provided from the ID. void element 19of the printer D. It will be recognized that the output signal from theemitter follower circuit 35 will be TRUE if the wrong combination signalor the void I.D. signal is present at the input. If this outputcondition exists it will inhibit the output signals from the no-errorNOR gate 36. If neither input signal appears at the emitter followercircuit 35, then, the output of the emitter follower circuit 35 will bein a FALSE condition so as to provide one of the input signals to theNOR gate 36 for satisfying the input conditions thereof. It will berecognized that with the absence of the wrong combination signal and thevoid l.D. signal, that these are the necessary conditions for signallinga valid key is present in the receptacle 12. No-error NOR gate 36 alsoreceives the decoded door I.D. signal from the scanning element C as aninput signal. The remaining input to the NOR gate 36 is the printcommand signal that is initiated from the printer D and inverted andapplied to the NOR gate 36 by means of the scanner control element 17,as will be more apparent hereinafter. At this point it is important tonote that if a void ID. and wrong combination signal is absent (FALSE)at the NOR gate 36 along with the print command and the decoded doorI.D. signal that only under these conditions will an output signal beproduced to trigger the one-shot element 37. The one-shot element 37 isessentially a timing element which allows a door to be held open whileallowing the scanning element C to continue scanning and prevent theprinter from printing out during the same dooropen period. For thispurpose, the one-shot output signal will persist on the order of 3 to 5seconds and apply its output signal to the OR gate 38. The resultingoutput signal from the OR gate 38, as a result of receiving the outputsignal from the one-shot element 37, will be applied to an OR gate 39.The other input signal to the OR gate 39 is the decoded I.D. signalreceived from the scanner 16. The presence of a signal from the OR gate38 at the inhibit input terminal of the OR gate 39 is effective foroverriding the door decoded I.D. signal applied to the individualinhibit gates of the inhibit gates 14 to thereby prevent the presence ofthe output indications at the gate 14 and to the printer D for printingout upon successive scanning of the same door under the same door-opencondition.

It should also be noted that the output signal from the oneshot 37 isindicative of a valid key present in the receptacle 12 and this signalis coupled back to the combination decoding element 13 for completingthe logical conditions necessary for operating the controlled latch 10.Stated difierently, the valid key signal derived from the one-shot 37 isactive for causing the valid key signal to appear at the output of thecombination decode element 13 and operate the controlled latch 10. The

other input signal to the OR circuit 38 is a signal provided by a key-intiming element 40. The key-in timing element 40 is responsive to akey-in signal directly derived from the receptacle 12. The operation ofthe key-in timer 40 is such that if the key is left in its receptacle 12for longer than a preselected time interval the key-in control element14 will provide a signal to the OR circuit 38 for inhibiting oroverriding the door l.D. circuit signals applied to the inhibit gates 14and prevent .the data bits from being coupled to the printer D. If thekey 11 is removed from its receptacle during the scanning interval thekey-in timer 40 is ineffective and the operation of the gates 14 foreach data bit is as discussed hereinabove, in response to a decoded doorl.D. signal received at the gate 39. The key-in timer circuit 40 maycomprise an RC timing circuit that is coupled to be responsive to akey-in signal from the receptacle 12 and to automatically time out forproviding the output indication in accordance with the selected timeinterval.

The output signal from the key-in timer 40 is also coupled to an ORcircuit 40-15. in parallel circuit relationship with the output signalsfrom the key-in timers for the remaining controlled doors. The outputsignal from the OR circuit 40-E may be applied to a door error lamp forvisually indicating the erroneous door condition. This does not identifythe door where the key-in condition exists and therefore the print outwould have to be examined to determine at which door the sameinformation has been printed out.

Now referring to FIG. 3, the detailed implementation of the scanner Cwill be examined. It should be appreciated from the above descriptionwith respect to FIG. 1 that the scanner C includes the scanner 16 andthe scanner control element 17 operative therewith. The scanner 16includes an oscillator 43 which may provide output pulses at the rate of20 milliseconds coupled to a NAND gate 44. The second input to the NANDgate 44 is derived from the scanner control element 17 and is normallyarranged in a high voltage state to allow the output pulses of theoscillator 43 to appear at the output of the NAND gate 44. This outputsignal may be inverted by a conventional NAND gate 45 before it isapplied to a two-stage binary coded decimal counter 46. The binary codeddecimal counter 46 comprises a first stage which has a ten-countcapacity and a second stage coupled thereto having a fourcount capacity.The first stage or units counter is identified as the counter 46U andthe second stage or tens counter is identified as a counter 46T. Thecounter 46 arranged in this fashion is defined to count up to 40 countsin accordance with the usual binary coded decimal counting techniques.The binary coded output signals from the counter 46U and 46T provide adifferent pattern of output signals in accordance with each of thecounts stored in the counter. It should also be recognized that when thecounter reaches its last count or the count of 39, it is recycled andthe counting sequence restarts at O. The operation of the counter 46 maybe signalled by the operational lights 47 coupled thereto asillustrated. The output of the counter 46 is coupled to a binary todecimal decoder 48 which receives the output pattern of binary codedpulses from the counters 46U and 46T and decodes it in terms of thedecimal system. The decoding of these signals by the element 48 willprovide a unique output signal from one of 40 output lines 39) from thedecoder 48. Stated differently, for each pattern of signals received bythe decoder 48 from the binary coded decimal counter 46, only one of the40 output leads from the decoder will be in a FALSE state. The 40outputs from the decoder 48 are defined for identifying the 40 doorsthat may be controlled in accordance with the present invention and areidentified as the doors 0 39. In this respect the 0 output from thedecoder 48 is applied to door 0 circuit at the OR circuit 39 therefor.In the same fashion, the l Output from the decoder 48 is applied to acorresponding OR circuit for the door 1 and the 2 output is similarlycoupled to the door 2 circuit. The same arrangement prevails for theremaining 37 controlled doors.

The scanner control element 17 is adapted for controlling the voltagelevel of the signal applied to the NAND gate 44 and thereby controllingthe pulsing of the counter 46 from the oscillator 43. For this purposethe scanner control element 17 includes the emitter follower circuits 50and 50A that are connected to be responsive to the key-in signal fromthe individual gate of the gates 14 unless it is inhibited by inhibitkey-in circuit 50B. The output of the emitter follower circuit 50A isapplied to a key-in" bistable element or flip-flop 51 which isresponsive to the reception of the key-in signal from the emitterfollower 50 to switch the flip-flop 51 into its low voltage state andtherefore prevent the oscillator pulses of oscillator 43 from beingapplied to counter 46. Specifically, the changing of the state of thekey-in flip-flop 51 prevents the input conditions at the NAND gate 44from being satisfied and therefore no output signal appears at the NANDgate 44 and no output appears at the output of the NAND gate 45 to pulsethe counter 46. Under these conditions the scanning operation is stoppedto allow the infonnation derived from the key in the receptacle to beprinted out. The key-in flip-flop 51 is reset by means of the printcommand derived from the printer D.'The print command signal will resetthe flip-flop 51 so that its output will again be in its normal highvoltage state and allow the pulses from the oscillator 43 to count upthe counter 46 and continue the scanning operation from door to door.

For the purpose of facilitating resetting of the key in flipflop 51there is provided an inhibit key-in control flip-flop element 52. This Kflip-flop gets its clock input from the output of the NAND gate 45 andits output connected to the inhibit key-in circuit 50B. This output isnormally in the low voltage state, thereby conditioning the flip-flop 51for the reception of the key-in signals. The set input of the flip-flop52 receives the print command from the inverter 53. The provision of theflipflop 52 is provided merely to inhibit the key-in command during theperiod from the beginning of the print until the falling edge of thesignal out of NAND element 45.

It should also be noted that the print command applied to the key-in"flip-flop 51 is also coupled by means of the inverter 53 as the inputsignal to the no.-error NOR gate 36 to the door circuits as illustratedfor the 0 door circuit.

The scanner control element 17 also includes a malfunction reset timer54 which functions as a watchdog timer for determining if a printcommand is received at the desired time intervals for resetting thekey-in flip-flop 51. If the print command is not received within thepredetermined time interval, the flip-flop 51 will be reset so that thescanning operation may continue. For this purpose the input to themalfunction reset timer 54 is coupled to the output circuit of thekey-in flip-flop 51 in common with the coupling of the flip-flopoutputsignal to the AND gate 44. The output of the malfunction reset timer 54is coupled to an input of the key-in flip-flop 51 to reset it in theevent the print command is not received from the printer D within theprescribed time interval, on the order of 2 seconds. The output of themalfunction reset may also be applied to an auxiliary flip-flop 55having its output coupled to a malfunction indicating light 56.Accordingly, when the malfunction reset timer provides a signal forresetting the key-in flip-flop 51 it will also reset the flip-flop 55and provide a visual indication of the malfunction of the printer D.

A further feature of the scanner control element 17 is the provision ofa daytime switch which allows the printer to be eliminated from the doorcircuits during the daytime, or during business hours, to prevent theunnecessary usage of paper while the business or room is open for thenormal course of business. The daytime switch may be a manually operatedswitch and is identified by the reference numeral 57 and is coupledbetween the print signal from the printer D or the one-shotmultivibrator 59 to the input of the flip-flop 51 by means of a delaycircuit 58 having its input connected to the emitter follower circuit 50and its output connected to a oneshot multivibrator 59. When the switch57 is in a normal position the print command will come from the printerD and while in the no-print position the command will come from theone-shot multivibrator 59 to let the scanning continue.

With the above structure in mind, then, the detailed operation of themultiplexer will be described. If there are no keys present in any ofthe 40 doors under the control of the multiplexer then the inputs to theNAND gate 44 will be satisfied and the pulses from the oscillator 43will be coupled directly to the counter 46 and the counter will bestepped through its 40 counts sequentially and re-cycled to O andcontinuously count the pulses applied thereto. During this interval thedecoder 48 will provide the scanning signals to each of the 40 doors todetermine whether or not a key is present in any of the 40 doors. If nokey is present in any of the doors the counter will continue to scansince the input conditions of the NAND gate 44 are continuously beingsatisfied.

If it is assumed that a key 1 l is inserted in one of the doors, then,during the scanning interval when the signal from the decoder 48 isapplied to the individual door circuit B having the key placed in itsreceptacle, a key-in signal will be transferred from the inhibit gates14 to the emitter follower circuit 50 for switching the state of thekey-in flip-flop 51. With the switching of the flip-flop 51, the NANDcircuit 44 input condition will no longer be satisfied and the counter46 will be halted. This causes the FALSE output signal for the decoder48 to be maintained in its FALSE condition and applied to the respectivedoor circuit B to allow the information to be derived from the key 11and to be processed to determine the validity or invalidity of the key.During this interval, then, the 1D. data bits are derived from theinhibit gates 14 and applied to the printer D. The 1D. data bits aredecoded by the ID. decoder 18 and examined by the ID. void element 19 todetermine the validity or invalidity of the ID. bits. The decoded 1D.data is applied to the print control 20 in combination with the key-in,door ID. and wrong combination signals for rotating the print wheels incorrect relationship to print out the decoded 1D. data, door 1D. data,etc. At this same interval, the combination" data derived from the keyreceptacle 12 is examined by the combination decode element 13 fordetermining whether or not the unlocking or combination data is correct.If the unlocking data is incorrect, a wrong combination signal will beapplied to the inhibit gates 14 and derived from the output of the gates14 and will appear at the print control element 20 as well. The wrongcombination signal from the inhibit gates 14 will also appear at theemitter follower circuit 35. A further signal with respect to theevaluation of the validity or invalidity of the ID. number may appear atthe emitter follower circuit 35. In the event that the key has a validID. number and a correct combination, a FALSE (zero) output signal willbe coupled from the emitter follower circuit 35 to the no-error NOR gate36. During this same interval, the decoded door signal and the printcommand will be present at the no-error NOR gate 36 so as to cause theoneshot door-open circuit 37 to be triggered and thereby apply a validkey signal to the combination decode element 13. This last indication ofthe information on the key 11 will cause the combination decode element13 to provide a valid key output signal therefrom for operating thecontrolled latch 10. It will, of course, be appreciated that in theevent that a void I.D. signal or a wrong combination signal is receivedat the emitter follower circuit 35 that a TRUE output from the no-errorNOR gate 36 will not be provided and therefore no valid key signal willbe coupled back from the door circuit to the element 13 therebypreventing the operation of the controlled latch 10. During theinterval, then, that the 1D. information is being decoded by the printerD and once the print wheels are in the correct position for a print outa print command signal is applied to the print hammer and is coupledback to the key-in flip-flop 51 to reset it and cause the counter 46 tocontinue its counting and thereby the scanning of the successive doors.If during the successive scanning intervals a key is maintained in itsreceptacle and it is once again sensed during successive scanningintervals, the key-in timer 40 will have been activated to provide anoutput signal at the OR gate 38. This signal will be applied as aninhibit signal to the OR gate 39 causing it to override the decoded doorsignal and therefore prevent the coupling out of the information fromthe inhibit gates 14 to the printer D. This condition will exist until akey is removed from the receptacle. A similar signal will exist if anelectrical condition that causes an equivalent'signal to a key-in signalto persist will exist until the electrical condition is removed. Thisprevents the printer D from continuously printing out the sameinformation in response to a single application of a key to itsreceptacle.

It should now be appreciated that the present invention has advanced thestate of the art through the provision of a multiplexing arrangementwherein a multiplicity of controlled accesses or doors may becontinuously scanned at a rapid rate for determining a key-in condition.In the event such a condition is sensed, the scanning is interrupted toallow the desired control infon'nation to be printed out by a timeshared printer.

What is claimed is:

1. A multiplexing system for monitoring and controlling the operation ofa multiplicity of controlled accesses, said system comprising aplurality of controlled accesses, each access having a latch andkey-operable control means for unlocking the latch and a key havingpreselected control actuation information recorded thereon unique foroperating the control means for unlocking the latch and preselectedidentification information having unique identification controlactuation information recorded thereon and means for indicating a key-incondition of the key relative to the con-' trol means for operating thelatter,

said key-operable control means being constructed and defined forunlocking the latch only in response to the placement of the key havingthe correct preselected control actuation information and the correctpreselected key identification information in the control means,

scanning means coupled to each of the controlled accesses forcontinuously scanning each access to sense the placement of a key in thecontrol means and producing a key in output indication representative ofa particular access having a key placed therein in response to thesensing of the key-in condition, recording means coupled to beresponsive to the key-in output indication of the scanning means forrecording the key information in terms of the identification of theaccess and the key control information, and

means for actuating said key operable control means to unlocksaid latchin response to said scanning means sensing the placement of a key in thecontrol means and producing a key-in output indication, said means foractuating said key operable control means operating to actuate saidcontrol means for a preselected duration of time during which access isprovided through the access associated with the actuated control meansand said scanning means operates to continuously scan said plurality ofaccesses.

2. A multiplexing system as defined in claim 1 wherein the scanningmeans includes scanning control means coupled to be responsive to thekey-in condition indicating means for momentarily stopping the scanningmeans in response to the placement of the key in the key operablecontrol means at each of the controlled accesses.

3. A multiplexing system as defined in claim 2 wherein said means foractuating said key-operable control means includes means for signallingthat a key having valid control actuation has been placed therein forunlocking the latch and providing an output indication of a preselectedduration for preventing the re-recording of the unlocked latch or key-incondition upon successive scans by the scanning means.

4. A multiplexing system as defined in claim 3 wherein the key-operablecontrol means includes timing circuit means coupled to be responsive tothe key-in condition indicating means and providing an output indicationafter a preselected time interval which is greater than said preselectedduration of said output indication of said means for signaling that akey having valid control actuation has been placed in said control meansthat the key-in condition persists to prevent the rerecording ofinformation at the corresponding access upon successive scans by thescanning means until the key-in condition is tenninated.

5. A multiplexing system as defined in claim 4 wherein the scanningmeans comprises an electronic binary counter and a pulse source coupledto the counter for continuously counting up the counter and resetting itto allow it to continuously recycle through its count in response to thepulses from the pulse source and having a binary decoder coupled toreceive the signals from the counter and providing a unique signalrepresentative of a controlled access for each count.

6. A multiplexing system for monitoring the operation of a multiplicityof controlled accesses, said system comprising a plurality of controlledaccesses, each access having a latch and an electrical key-operatedlatch control means for locking and unlocking the latch, said controlmeans including circuit means for determining whether a key coupled tothe control means is a valid key or not for unlocking the latch andsignalling the validity or invalidity of the key, a correspondingplurality of electrical keys each having unlocking information recordedthereon and derivable therefrom upon being coupled to the latch controlmeans, an electronic scanner having a plurality of output indications,one for each controlled access, for continuously sensing the coupling ofan electrical key to the latch control means at each of the controlledaccesses and to momentarily interrupt its scanning in response to thesensed coupling of a key with the latch control means and to provide anoutput indication representative of said condition,

recording means coupled to be responsive to the scanner and the latchcontrol means for recording the coupled key unlocking information anddetermining as to whether or not the coupled key is valid or not for thecontrolled access,

and means for actuating said latch control means to unlock said latch inresponse to said electronic scanner sensing the coupling of a key withthe latch control means, said means for actuating said latch controlmeans operating to actuate said control means for a predeterminedlength-of time during which access is provided through the access 1Qassociated with the actuated latch control means, said scanner operatesto continuously scan said plurality of accesses and said recording meansis inhibited from recording the coupled key unlocking information morethan once.

7. A multiplexing system as defined in claim 6 wherein the recordingmeans is a printer including means for rendering certain valid keys voidand providing an output indication to said latch control means upon thecoupling of one of said voided keys to the control means for renderingthe key invalid for unlocking the latch.

8. A multiplexing system as defined in claim 7 wherein the electricalkeys having unlocking information and identification informationrecorded thereon and the latch control means is defined for unlockingthe latch only when a key coupled thereto has valid unlocking and valididentification information recorded thereon.

9. A multiplexing system as defined in claim 8 wherein said means foractuating said latch control means includes circuit means for signalingthe coupling of a completely valid key to the control means to allow theunlocking of the latch and preventing the repetitious printing out ofthe key information during said predetermined length of time that saidcontrol means is actuated upon successive scans of the controlledaccesses until the key is decoupled therefrom.

10. A multiplexing system as defined in claim 9 wherein said means foractuating said control means includes timing circuit means responsive tothe coupling of a key to the latch control means for rendering theprinter inoperative for the access having a key coupled thereto beyond apreselected time interval which is greater than the predetermined lengthof time that said control means is actuated.

11. A multiplexing system as defined in claim 7 wherein the printerprovides an output printing signal and the electronic scanner includescontrol means responsive to the printing signal for causing the scannerto continue scanning in response thereto.

12. A multiplexing system as defined in claim 11 wherein the controlmeans includes circuit means for sensing the printer malfunction andproviding an output signal for causing the scanner to continue inoperation in response thereto.

1. A multiplexing system for monitoring and controlling the operation ofa multiplicity of controlled accesses, said system comprising Aplurality of controlled accesses, each access having a latch andkey-operable control means for unlocking the latch and a key havingpreselected control actuation information recorded thereon unique foroperating the control means for unlocking the latch and preselectedidentification information having unique identification controlactuation information recorded thereon and means for indicating a key-incondition of the key relative to the control means for operating thelatter, said key-operable control means being constructed and definedfor unlocking the latch only in response to the placement of the keyhaving the correct preselected control actuation information and thecorrect preselected key identification information in the control means,scanning means coupled to each of the controlled accesses forcontinuously scanning each access to sense the placement of a key in thecontrol means and producing a key-in output indication representative ofa particular access having a key placed therein in response to thesensing of the key-in condition, recording means coupled to beresponsive to the keyin output indication of the scanning means forrecording the key information in terms of the identification of theaccess and the key control information, and means for actuating said keyoperable control means to unlock said latch in response to said scanningmeans sensing the placement of a key in the control means and producinga key-in output indication, said means for actuating said key operablecontrol means operating to actuate said control means for a preselectedduration of time during which access is provided through the accessassociated with the actuated control means and said scanning meansoperates to continuously scan said plurality of accesses.
 2. Amultiplexing system as defined in claim 1 wherein the scanning meansincludes scanning control means coupled to be responsive to the key-incondition indicating means for momentarily stopping the scanning meansin response to the placement of the key in the key operable controlmeans at each of the controlled accesses.
 3. A multiplexing system asdefined in claim 2 wherein said means for actuating said key-operablecontrol means includes means for signalling that a key having validcontrol actuation has been placed therein for unlocking the latch andproviding an output indication of a preselected duration for preventingthe re-recording of the unlocked latch or key-in condition uponsuccessive scans by the scanning means.
 4. A multiplexing system asdefined in claim 3 wherein the key-operable control means includestiming circuit means coupled to be responsive to the key-in conditionindicating means and providing an output indication after a preselectedtime interval which is greater than said preselected duration of saidoutput indication of said means for signaling that a key having validcontrol actuation has been placed in said control means that the key-incondition persists to prevent the re-recording of information at thecorresponding access upon successive scans by the scanning means untilthe key-in condition is terminated.
 5. A multiplexing system as definedin claim 4 wherein the scanning means comprises an electronic binarycounter and a pulse source coupled to the counter for continuouslycounting up the counter and resetting it to allow it to continuouslyrecycle through its count in response to the pulses from the pulsesource and having a binary decoder coupled to receive the signals fromthe counter and providing a unique signal representative of a controlledaccess for each count.
 6. A multiplexing system for monitoring theoperation of a multiplicity of controlled accesses, said systemcomprising a plurality of controlled accesses, each access having alatch and an electrical key-operated latch control means for locking andunlocking the latch, said control means including circuit means fordetermining whether a key coupled to the control means is a valid key Ornot for unlocking the latch and signalling the validity or invalidity ofthe key, a corresponding plurality of electrical keys each havingunlocking information recorded thereon and derivable therefrom uponbeing coupled to the latch control means, an electronic scanner having aplurality of output indications, one for each controlled access, forcontinuously sensing the coupling of an electrical key to the latchcontrol means at each of the controlled accesses and to momentarilyinterrupt its scanning in response to the sensed coupling of a key withthe latch control means and to provide an output indicationrepresentative of said condition, recording means coupled to beresponsive to the scanner and the latch control means for recording thecoupled key unlocking information and determining as to whether or notthe coupled key is valid or not for the controlled access, and means foractuating said latch control means to unlock said latch in response tosaid electronic scanner sensing the coupling of a key with the latchcontrol means, said means for actuating said latch control meansoperating to actuate said control means for a predetermined length oftime during which access is provided through the access associated withthe actuated latch control means, said scanner operates to continuouslyscan said plurality of accesses and said recording means is inhibitedfrom recording the coupled key unlocking information more than once. 7.A multiplexing system as defined in claim 6 wherein the recording meansis a printer including means for rendering certain valid keys void andproviding an output indication to said latch control means upon thecoupling of one of said voided keys to the control means for renderingthe key invalid for unlocking the latch.
 8. A multiplexing system asdefined in claim 7 wherein the electrical keys having unlockinginformation and identification information recorded thereon and thelatch control means is defined for unlocking the latch only when a keycoupled thereto has valid unlocking and valid identification informationrecorded thereon.
 9. A multiplexing system as defined in claim 8 whereinsaid means for actuating said latch control means includes circuit meansfor signaling the coupling of a completely valid key to the controlmeans to allow the unlocking of the latch and preventing the repetitiousprinting out of the key information during said predetermined length oftime that said control means is actuated upon successive scans of thecontrolled accesses until the key is decoupled therefrom.
 10. Amultiplexing system as defined in claim 9 wherein said means foractuating said control means includes timing circuit means responsive tothe coupling of a key to the latch control means for rendering theprinter inoperative for the access having a key coupled thereto beyond apreselected time interval which is greater than the predetermined lengthof time that said control means is actuated.
 11. A multiplexing systemas defined in claim 7 wherein the printer provides an output printingsignal and the electronic scanner includes control means responsive tothe printing signal for causing the scanner to continue scanning inresponse thereto.
 12. A multiplexing system as defined in claim 11wherein the control means includes circuit means for sensing the printermalfunction and providing an output signal for causing the scanner tocontinue in operation in response thereto.